1. Field of the Invention
This invention relates to process for treating a molded, porous carbon article, and more particularly to a process for lowering the surface frictional resistance of a molded, porous carbon article for use as a sliding material, etc., thereby improving the sliding durability, etc. of the article
2. Description of Prior Art
A molded carbon article, when used as a sliding material, etc., shows much abrasion and generates a large amount of abrasion powder. Thus, its use is restricted. If the surface friction coefficient of the article can be lowered, such problems may be solved, and also if the thickness of the layer treated to lower the surface friction coefficient can be increased, the durable time may be increased.
Heretofore, a solid lubricant such as molybdenum disulfide, etc. has been used to lower the surface friction coefficient of a molded carbon article. The solid lubricant is effective during the initial period of use, but no continued effect can be extended for a long time. Furthermore, the molded carbon article is liable to be pulverized and scattered, resulting in fouling. In this respect, its use is also restricted.
To lower the surface frictional resistance of a molded rubber article for use also as a sliding material, etc. like the molded carbon article, it is disclosed in Japanese Patent Application Kokai (Laid-open) No. 56-126,146 to treat the surface of a molded rubber article with a fluorine gas or a fluorine gas diluted with an inert gas. When this treatment is applied to a molded, non-porous carbon article in the same manner as for the molded rubber article, no desirable effect can be obtained, as will be shown in Comparative Example 1 which follows.
Furthermore, it is likewise disclosed in Japanese Patent Publication No. 54-36630 to treat the surface of a molded rubber article with antimony pentafluoride. When this treatment is applied to the surface treatment of a molded, porous carbon article, no effect can be obtained at all, as will be shown in Comparative Example 2 which follows.
Still further, it is disclosed in Japanese Patent Application Kokai (Laid-open) No. 53-130,327 to embed a carbon fiber-filled carbonaceous vessel in a molten salt electrolytic bath of acidic hydrogen potassium fluoride (HF.KF), conduct electrolysis of the molten salt while using the carbonaceous vessel as an anode, and introduce a fluorine gas generated at the anode in between the carbon fibers, thereby fluoridizing the surface layers of the carbon fibers. When this treatment is applied to a molded, porous carbon article, no desirable surface treatment can be obtained due to too vigorous fluorization reaction on the contrary.